The present invention relates to an exhaust gas processing device for a diesel engine and specifically to an exhaust gas processing device for a diesel engine which can carry out sufficient regeneration processing of a DPF.
In the present description and the claims, DPF refers to a diesel particulate filter, PM refers to particulate matter in exhaust gas, and DOC refers to an oxidation catalyst.
Conventionally, there has been proposed an exhaust gas processing device for a diesel engine, the device including: a DPF; a PM accumulation amount estimating section for estimating an amount of PM accumulated in the DPF; a DPF regeneration section; a DPF regeneration control section; a storage section; and an accelerated regeneration requiring information notification section. When a PM accumulation estimate increases to a normal regeneration starting determination value, the DPF regeneration control section automatically starts normal regeneration processing by the DPF regeneration section to increase a temperature of exhaust gas to be passed through the DPF. Then, at the time of determination for accelerated regeneration requirement, when the PM accumulation amount estimate is equal to or higher than an accelerated regeneration requirement determination value, the DPF regeneration control section carries out notification of accelerated regeneration requiring information by the accelerated regeneration requiring information notification section. After the accelerated regeneration requiring information is notified, when an accelerated regeneration starting operation section carries out accelerated regeneration starting operation, the DPF regeneration control section switches from the normal regeneration processing to accelerated regeneration processing by the DPF regeneration section to increase the temperature of the exhaust gas to be passed through the DPF to make regeneration speed of the DPF higher than that in the normal regeneration (see FIGS. 1 and 2 of Japanese Patent Laid-open Publication No. 2011-32943, for example).
This type of exhaust gas processing device for the diesel engine has an advantage that the regeneration of the DPF can be finished quickly by the accelerated regeneration when it takes time to regenerate the DPF by the normal regeneration, which suppresses reduction in fuel efficiency and reduction in output due to extension of the regeneration processing of the DPF for a long time period.
However, when the accelerated regeneration starting operation section does not carry out the accelerated regeneration starting operation after the accelerated regeneration requiring information is notified, and if the DPF regeneration control section continues the normal regeneration processing by the DPF regeneration section, it may cause a trouble.
Regeneration of the DPF may end when it is incomplete.
When the accelerated regeneration starting operation section does not carry out the accelerated regeneration starting operation after the accelerated regeneration requiring information is notified, and if the DPF regeneration control section continues the normal regeneration processing by the DPF regeneration section, a condition for ending the normal regeneration such as continuation of an exhaust gas temperature equal to or higher than 500° C. for a predetermined time period may be satisfied, even though a substantial amount of PM is accumulated in the DPF and the accumulation amount of the PM has not sufficiently decreased, and the regeneration of the DPF may end when it is incomplete.